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Ah. Thanks a lot for that. Aye coming from a belt driven build too so something more stiff is in order this time. Yep the rack and pinion sounds like a perfect solution for that size (that's a big machine, jealous) this one has a cutting area of around 1100mm x 750mm ish but should be big enough for my needs. I do a lot of aluminium work and bits of hardwood so don't need anything too large. You never know i might go for an 8x4 machine down the line.
Bigger machine needs a lot more space to be usable. This is my downfall. I may well downsize her and go for a 4 or 5 axis design. I'm getting the Itch !!!!!!!!!!!!!!.
I've had a smaller machine than mine for quite a few years, with a cutting footprint of roughly 500 x 380mm and have not found that to be too limiting generally speaking, so didn't want to go too large. If I were to go 8x4 I think I'd go vertical like Jazz's to save space and help with chip clearing. I want to leave some room in my workshop for some other bits too. I acquired an old CNC lathe (EMCO) that I'm upgrading and I'd like to build a small plasma table at some point (maybe 2x4). We'll get this one done firstly anyway.Quote:
Originally Posted by Mister Mills
A rotary axis would be great, if you could pull off a 5 axis design I'd be very interested to see that come together.
I may well downsize to 1m x 1 m or 1m x 1.2m. Seriously Don't have the room and no real need for the full size setup. It took me 6 months to build the Big girl! and if I am to be honest I don't know why I went so big. The joy for me was building her but she has never had a full sized sheet of anything on the table!!!!!!!. If I go 1 x 1.2(Cutting) I will arrange it so I can slide a full size sheet into and through her to save cutting it into several smaller pieces. I have a few smaller ball screws that might fit the new proposed dimensions and I would prefer to use those instead of the R&P. This time round I will Catalog the build :). I have some holiday time booked in 2 weeks so I might start the strip down then. Fingers crossed!
Ah here. It never ends. But I bet the next one you build will be better. My first one was an mdf abomination, second much better, and this much much better (so far) we'll see what happens. I'd never go away from propper linear rails again though, anything else is just a false economy in my book as you spend so much time messing you'd be better to buy something made for the job upfront and save the hassle.
I've been busy planning the base, but work is busy atm so I won't update just yet. Bits and pieces are on route but ill post info soon to that end.
I totally agree about the rails. Mine came from a salvaged Bisse industrial cnc router. Top quality parts. Budget usually decides @ 3 meters long! I'm going to try and sell my 50W 600x500 laser cutter/engraver so that might help with the proper rail requirement. Doing a check list at the moment and I have everything I need. Says me as I blindly walk into this project. No doubt there will be something missing when I get to that point of" Shit I forgot about that! .
The size will be dictated by the ball screws i have (they came from a Salvaged Datron cnc machine) top notch. The 5 axis setup is really something I would like to do but I will start with 3 and keep the other 2 in mind when doing the new re-design. Good luck with the new base and be sure to post some photos.
Planning is in the works for the base, I've been collecting materials here and there as I can source them in the current climate. I've decided against the wall mounted option, when I drew it up in CAD it wasn't really saving me a massive amount of floor space (due to the relatively small footprint of my machine) and I really want to make use of high flow flood coolant so felt a regular horizontal setup would be best.
I've decided to be a bit unconventional with this design as outlined in the images.
Attachment 28144Attachment 28145
The main sides of the structure will be made from concrete based blocks, each measures 140mm(H) x 212mm(W) x 442 (L) and are very strong. These blocks are common here in Ireland and are largely made from a high proportion of granite aggregate along with a minimal amount of concrete as a binder (I'd estimate 15 - 20% concrete/cement) and I hope in this case, given the ratio of granite to cement, that shrinkage will be quite low and vibrations can be minimised too. I've had these blocks for over 12 months now so they should be relatively stable, but time will tell I suppose.
The intention for the main table surface is to cast this from home made glass fibre reinforced ultra high performance concrete. The intention is to cast this as a 75-100mm thick section in one pass by supporting the open section with ply braced from underneath (pre cut in the middle and siliconed at the joint for easy removal). I have sourced and received the glass fibre strands and the superplasticiser which I'll use to minimise the water content required in the concrete mix. I also intend to embed typical steel reinforcements (rebar or mesh or a combination of) I have yet to source those aspects as local steel outlets are closed for the next week or two. Time wise it's likely to be around the second week of June before construction can start, I'm looking forward to it.
For wiring/routing I intend to cast some 30-40mm plastic conduit (sink drainage pipe) into the front section, to allow motor and limit switch wiring to be routed cleanly from the left side to right. Controls box for the steppers and spindle VFD will mount to the exterior of the right hand wall.
I've been experimenting with some cast concrete of late and some alterations in mixes and proportions, likely I'll keep it fairly simple but I'll make some test samples soon to test those out.
The top of the table will be certainly quite rough post concrete casting, so the intention I have is to allow the concrete some time to settle and after that period level the entire table top with a 3mm layer of epoxy to give a nice flat surface to measure from and secondly, to provide some waterproofing. Part of the idea of designing the base this way is to allow sufficient space for a flood coolant capture tank to be housed in the underside of the 'table' and further design some fluid direction system once a tank has been sourced.
I could obviously go the tried and tested route and build the base from steel or aluminium, but I'd like to try this out to see how it goes. It's relatively cheap and if it all goes tits up, well I'm sure I can get a sledge hammer handy enough.
Good stuff John. I would have never thought of a concrete base but now that I see you mock up it makes perfect sense. It will also be much easier to surround the upper part of the walls with a side/back etc to catch coolant. Flood coolant it a really good thing to have on any machine cutting aluminum. It will save toy a ton of cutters! Good luck with the build.
That's a really interesting base design, I've been wondering about a concrete or block base myself in the future as a cost-effective and very rigid structure. I'll be interested to follow your progress.
If you plan to drain the coolant to a tank underneath then it may help to cast a short length or two of plastic drainpipe through the base to act as conduits for the fluid hoses.
Thanks, yes I think it should work out okay. I'm doing some calculations for mixtures at the moment in the hope to test the mix out this weekend in a very small batch. The only unknown is the shrinkage of the mortar for the walls/block but I'm hoping with a solid UHPC top any shrinkage should even out each side or be small. I'll try to get away with as little mortar thickness as possible but may test the Glass Fibre Reinforced mix as a mortar first to see if it bonds okay.Quote:
Originally Posted by Mister Mills
I'll upload sources etc when I get the initial test done.
We'll see how it works, I can't see why it will be a major issue unless shrinkage is significant over time, but I'll give it a bash. That's a good point on the drainage, I'll have to reiterate the CAD some more. The general idea was to have the coolant flood over both front and back and design a fibreglass chute to direct fluid back to the tank but that could also work, I'll have to have a think.Quote:
Originally Posted by Kitwn
Just thinking out loud here John, but once you have the base epoxied up for leveling the rails you might as well use that surface as the base of your coolant-catching tray with a drain down to a storage tank below. Maybe build up the surface to direct the fluid to the drain. Rather like an Australian bathroom where the entire floor is built up round the outside to direct any spilled water into a central drain.
Hey, I think I'm following what you mean, that's not a bad idea actually, thanks. What I could do is run channels at the sides down into pipework and into the catchment tank from there, rather than fluid running over the front and back, and build a lip at the front and back for liquid catchment. That might make things a bit difficult loading and unloading stock though, particularly if stock is to overhand the Y (I do that sometimes).Quote:
Originally Posted by Kitwn
The spindle only gets within 150mm or so of the alu sections which holds the rails left and right so there's plenty of space there for a liquid channel. I must draw up some options to gauge the simplest approach before starting.
Initial test mix is done, the testing here is designed to judge bonding strength when using a simple UHPGRFC mix as a replacement for mortar. This might be unnecessary but mixes like this are said to be good for 12,000psi or so, so I'd like to try it.
UHPGFRC mixes (in my very limited experience) are approached differently than regular cement type mixes, insofar as the cement to aggregate (sand) proportions are quite different. With regualar cement mixes you would generally be 1:3 cement to sand ration, here we are 1:1 roughly.
I have a simple mix and a more exotic one, the simple mix is approached here as I'll need to source some other part for the latter which I'll detail later.
Here we have:
Attachment 28150
+200g Sharp Sand (quartz I believe) I live near several quarries and this stuff costs me roughly 25 euro per tonne, give or take, and makes great concrete.
+200g Portland Cement (regular cement). Generally this will be mixed with other elements such as 20% CSA or Silica Fume, I'll fill you in on that later, those can be hard to source.
+6g of Glass Fiber (From mbfg.co.uk added to the mix last, strand length is 13mm in this case, probably too long but it'll do the job)
+0.6g of Plasticiser (FLUP PCE 104 from moertelshop.de) I went with the manufacturers recommendation in this case of 3g/kg, it probably needs to be doubled in reality though, so I'll have to order another 1kg tub for the table to be sure.
Don't take anything I say as gospel, this is what works for me so far, I'm very new to this so take everything with a pinch of salt and as 'in testing'.
The mixing procedure used was pretty straightforward, mix sand and cement together dry first, add a small amount of water to make an overly dry mixture that is just starting to clump a little. Add super plasticiser, continue to mix for a minute or two (vigorously) and add more water to bring it to field capacity being careful not to overdo it. When the consistency was where I wanted it, I mixed in the glass fibers last.
I ended up using a little more water than I would have liked or predicted from my calculations (65g), but I think I'll double the plasticiser next time and test again to see if I can further reduce the water input.
Attachment 28149
I used some small 'soap bar' bricks which are almost identical in nature to the larger versions to test it out, at the moment I'm mainly concerned with bonding strength if I use it as a mortar between the blocks. If it fails to bond, I plan to make another custom mortar mix using standard mortar mix with sand, cement lime and mortar plasticiser with some added glass fiber reinforcement to beef it up as I know that will stick well to the blocks.
One thing I've noted is that the mixture consistency becomes noticeably more 'dry' when adding the Glass Fiber, so I'll have to balance that out. Also the working time is short, around 20 minutes, so I'm going to have to be on the ball when doing this but I have a cement mixer so it should be doable.
The mixture is curing very fast, so in a day or two I should have an idea how the bonding is.
Some small progress.
After letting the GRFC mortar test cure for a week in situ in my workshop I inspected it for bonding, the very scientific method of slapping it with a hammer was employed. I was mostly concerned initially with whether it would bond significantly to each brick but I'm confident now that it will be perfectly fine in that regard. It's clearly much stronger than regular mortar and I'd expect it to shrink less and be stronger in compression. That's good enough for me to move on.
One thing I realised after purchasing the glass fibre and mixing up this test is that AR glass fibre is recommended as it is suitable for the extreme environment of usage in concrete (general E glass is not as it is attacked by the alkalinity). After reviewing the technical documents from the supplier though it seems that this isn't a major issue for me, luckily. The glass fibre I have purchased, whilst not AR glass, the type I have (E6-CR from Jushi Tech http://en.jushi.com/res/excel88fcd3bf87268a79.pdf) is tested and recommended in both high acid and highly alkaline situations so it should be fine. I note it here for others though, be careful, glass fibre is not all suitable here and go for something that is specified for concrete usage.
Here's a picture of the GFRC mortared test, being reused as a weight. This mortar is tough stuff. I'd like to do some more scientific tests before casting the main bed, I'll get the walls up firstly.
Attachment 28207
I'm pretty slammed at work but had some time to layout the basic structural outline on my newly concreted floor. Nothing too complex, four bricks, some string and some careful corner to corner measurements to make sure it was square. One of the issues I was having with the concrete floor was it was endlessly dusty, no matter how much it was swept it kept producing more and more dust. I treated it once with a PVA based sealer and water and this has cut this down. I will aim to treat it once more before moving on with the block work next week. This should also help ease my mind around bonding to the floor, I was more than a little concerned that it wouldn't bond correctly due to the dust but I'm told this is a commonly used solution to aid bonding.
Attachment 28208
Next step for me is to get my workload tied off and begin on this around the 10th.
I've ordered some new motor to ballscrew connectors some months back but they have yet to arrive, if anyone knows of a reliable UK source I'd appreciate it. I'm looking for something to handle 480oz/inch with minimal backlash. 8mm to 12mm. Without a lathe in situ I can't really modify what I have accurately and haven't as yet been able to fully test the new ballscrew install.
Anyway, that's it from me for now, more soon.
Hey John,
I have 3No 8mm to 12mm couplers on the way. They should be with me in the next few days. I have no need for them as they were part of a package deal. I have upgraded my motors to Nema 34's and I have ordered the 12 x 14 Couplers that I need. You would be more than welcome to have the 8 x 12's for nada... Otherwise they will just sit in a box for eternity.
Hey, that's very kind I appreciate that, I might take you up on that if you really don't mind. I've ordered two pairs actually but this whole pandemic seems to have put a spanner in the works to getting anything from China. I'm not in a mad panic but if there's nothing next week can I give you a shout? I'm happy to fire some money over for them.Quote:
Originally Posted by Mister Mills
No problem John,
They are still on the way for me. Currently in Germany so I would expect them at some stage next week. Looks like I am going to be waiting for my new motors and drives a while more than I thought also due to C19. It's a pain in the ass. I'm drooling over that piece of level floor in your workshop. I'm building on a ski slope at the moment hahaha
[QUOTE]I treated it once with a PVC based sealer and water and this has cut this down. I will aim to treat it once more before moving on with the block work next week. This should also help ease my mind around bonding to the floor, I was more than a little concerned that it wouldn't bond correctly due to the dust but I'm told this is a commonly used solution to aid bonding.
[/QUOTE
Looking good, I take you meant PVA or even better is SBR
[QUOTE=Clive S;117646]I did yea, thanks I didn't even notice that error (edited) it must have been the autocorrect. I'll look up SBR before beginning as I'd like to treat it again if they are compatible with one another. Thanks for the heads up.Quote:
I treated it once with a PVC based sealer and water and this has cut this down. I will aim to treat it once more before moving on with the block work next week. This should also help ease my mind around bonding to the floor, I was more than a little concerned that it wouldn't bond correctly due to the dust but I'm told this is a commonly used solution to aid bonding.
[/QUOTE
Looking good, I take you meant PVA or even better is SBR
Okay,
So a bit of progress. I slowly managed to get the walls built for this machine base. I ended up mixing small batches of my previous glass reinforced mortar mix, essentially just scaled up to larger batches and continued building one layer at a time, leaving a couple of hours between layers to allow mortar to go off slightly.
I ended up with 3.5 blocks long per layer and five layers high in total, to bring it roughly to waist level. I began by pre-cutting the granite/concrete blocks with a diamond disk on the 4" grinder and cut around the circumference in the centre, blocks were then easily separated into pretty clean halves through some brute force with a bolster and club hammer. It doesn't take a huge amount of effort in reality. I certainly won't win any awards for my block laying skills, but this mortar is more difficult to work with tidily than regular mortar due to the glass fibre input. It should be worth the effort I feel as it is tough stuff, so I don't see any issues with it. It should mostly be under compression here so hopefully shrinkage will be a non issue later. We'll see I suppose.
I tended to try and keep the mixture on the drier side. It is more difficult to manage that way but I feel this will be a good approach in terms of the overall strength. The water volumes are only a guideline really, in practice each batch will differ slightly so half is added, and gradually added there after to avoid making it too wet. With the super-plasticiser it's easy to overshoot the water addition and end up with a mix which has too much flowability.
Attachment 28379Attachment 28381Attachment 28380
I ended up leaving some space around the perimeter in order to facilitate access and to allow sufficient room for any future enclosure.
Attachment 28383Attachment 28382
Thanks Clive for the heads up on SBR, I've purchased a gallon of that to treat the floor and paint it later. I'll likely get the messy 'table-top' casting out of the way before I do that though. That's the next job on the list.
Not long now John........... Looking pretty sturdy! I have been goosed for time myself but have started do do a few bits as stuff arrives. Delivery times are dreadful :(
Ah, it's slowly taking shape. Thanks Liam. Can't imagine it's going to fall over any time soon so I'm pretty happy it worked out. Next job is sourcing some plywood and steel rebar so I can prep a mould to cast the top. All being well I hope to get started on that this weekend if I can get everything I need. I'll need to buy some more cement and check on the status of my plasticiser order, it should be here soon.
I ended up ordering some more motor couplers from a European source this time, third time I've ordered these similar parts now which has been both annoying and unnecessarily costly but I don't hold much hope of anything I've ordered from China ever arriving to my door. I'm a cynic in general but part of my thinks this whole thing is really about putting a pin in Chinese manufacturing dominance. Maybe that's a good thing for us and this particular interest but anyway, maybe I'm just getting too cynical as I get older.
Anyway, if this order doesn't come through I'll definitely hit you up about those couplers again if they come through to you. I'm hoping mine will be here in the next few days so I can finally test the ballscrew install.
Hi John, My order arrived last week. A month late!!!!!!!!!!!! I have 3 pcs of spare 8 to 12 mm couplers. PM me your details and I will pop them in the post if you still need them.
My motors and atc wont be here for another 3 weeks at least :( so I well know how much of a pain it is to be waiting for stuff to arrive.
I agree with the whole cynical outlook. It's true haha. Same myself.
Thanks, I'll give these ones a few days and if nothing by the end of the week I'll give you a shout. The first order I placed was at the start of April so I doubt they're disappeared somewhere at this stage. Thanks a lot though!
More progress made over the weekend. I didn't quite get to the table top pouring but have the majority of the prep done. I also received the ballscrew to motor mounts (finally) so was able to install and test those. No issues so far, noise is greatly reduced and I have it running up to 6 meters/min currently. Beyond that I get stalling but may be able to tweak it a little more later.
Next step in the table build was to build a mould for the concrete top which will be cast soon. I'm awaiting some more super plasticiser but that should be here soon. Calculating the approx weight it will be in the order of 400KG when cast, so my first concern was bracing the open section well.
Attachment 28433
I chose to use studding which was left over from the building of the workshop in which this machine resides. I made up three sets of braces one for each side and a beefier version for the middle section. I chose to do this with the consideration that it needs to be knocked out from underneath later: I want it to be solid but also removable after the fact. There were some additional braces between these sections that isn't shown here.
On top of this some 11mm ply was set and sealed with silicone between joints. I chose to have the ply a little lower than flush with the walls, this might be difficult to see in the photographs but the idea is that the concrete pour will step down 10mm (vertical) over the end of the block walls before meeting the ply on the inner side of the blocks, creating a key of sorts. I thought this would add some additional strength.
Attachment 28434
Toward the front I added some 34mm (I think) plastic conduit so I can cleanly route a few wires from left to right (front left Y motor and home/limit switch). This is cut to be a tight push fit against the ply walls, which are fixed to the walls with masonry nails and a 600Kg ratchet strap is added for additional support from bowing. I also ran some lengths of string through the conduit/pipe and fed these through the ply walls at each end such that I can easily pull my wiring through post casting later.
Attachment 28435
All the wooden surfaces that will be removed were given a couple of coats of beeswax to function as a release agent to aid removal post concrete pour.
Attachment 28436
Lastly, high tensile steel rebar was added in an overlapping cross pattern. I chose to tack weld these together with the ARC welder and prop them up towards centre (ish) with some rock that can stay in situ as I cast.
Attachment 28437
I've got a few little gaps here and there to fill with silicone but as soon as the plasticiser arrives I should be good to go on the casting of the top section. I roped my brother in law to help out, likely it will be Saturday next when I get started on that bit.
Not sure if anyone's still following along, but I'll pop stuff in here regardless for sake of completion.
Concrete top has been poured. All in all it wasn't very difficult with the help of my brother in law and a cement mixer. I ended up pouring just over 500KG of my initial glass fibre mix scaled up. I was a bit nervous that the mould wouldn't hold up to the pressure/weight, but it seems to be okay (touch wood).
Just for reference, the mixer held:
50KG of sand
50KG cement
to this I added:
150g of super plasticiser
1.5KG of glass fibre
circa 8L of water, added gradually to play the mix by ear a little.
I ended up with five of these mixes in total in this top section. I don't envy the person that has to remove this, and hope that it isn't me....
Attachment 28486Attachment 28487
I've covered this in plastic sheet (not shown) to prevent it from drying out too quickly so that it can cure properly and I'm going to have to give this a mould at least a week before touching it. What I'll likely do is leave the mould sides in place and cast the epoxy top before removing the sides. I do need to do some careful figuring out to maximise the use of my z travel though. There may be a case where I'll have to increase the height of the Y rails to this top to give me sufficient clearance to fit my vice etc. but that is to be determined and most likely unnecessary.
Don't worry. The next owners of the house can turn it into a poole table :excitement:Quote:
Originally Posted by Evengravy
Looking forward to seeing the final machine and how you make the gantry to match the base.
That's a good point! Next up epoxy layer, I'm still looking around for materials atm. If anyone has any heads up on a low viscosity resin I'd appreciate it. I used one years ago on the Momus CNC base but completely forget the manufacturers name. I'm sure I'll find something though.Quote:
Originally Posted by Kitwn
Wests system https://www.westsystem.com/the-105-s...ins-hardeners/Quote:
Originally Posted by Evengravy
Thanks Clive, I'll take a look at that one.
Coming along nicely John. I really looking forward to seeing her up and running. :)
.
Me too! It's been a long time but we'll get there. I'm actually pretty glad I did the wiring aspect earlier, I think that the thought of tackling that again right now would be overbearing.
The top is drying well but not as flat as I would have liked, there is an area in the centre where the concrete is 5mm or so lower than the rest, I'm not entirely sure if it was bowing under the weight or just due to some factor related to drying but it's not the end of the world.
I have sourced the resin, it's here with me, I ended up going to a crowd in Northern Ireland but I'll fill in details later around that.
Prior to pouring the top I intend to flatten it as much as possible, reason being the resin isn't cheap and I want to have a nice even layer across the surface. To that end I have ordered a Diamond Cup for grinding/polishing concrete that will fit to my 4" grinder. It's on the way so should be here soon. It shouldn't take too much effort to knock down the high spots of the top with this tool to prepare it for the epoxy layer. I might combine the grinding with some filling of the very low area with epoxy/granite to minimise grinding but we'll see how we go.
I have a good respirator and will likely try to work wet with the grinding if possible, I know silicosis from breathing concrete dust is nothing to toy with. I really would have liked to have avoided grinding the top but those are the breaks, it will all work out I'm sure. As soon as the grinding disk arrives I'll be getting started.
One thing I'm a little concerned with in relation to the epoxy pour is the temperature in the workshop, looking at the resin data sheet we need to stay above 15 deg. C to avoid issues. I'll have to plan ahead with weather and some external heating source (heat lamp maybe) but I'll have a think, I'm sure we can come up with something.
You might be better off trying self leveling floor compound, it runs like water.
Regards
Mike
Thanks Mike, I'm kind of committed to this way of approaching it now as I have all the bits and bobs ordered. The resin I have is really low viscosity so it's really just a case of roughly evening the concrete surface before hand, shouldn't be a massive chore but without doing so the majority of the resin would sit in the centre leaving an overly thin layer at the sides where the rails will sit. It's not far off as it is though, about 5mm in the worst spots so it'll be fine with some gentle massaging. Appreciate the point though, I might source some of that to level any low spots on the floor of the space itself before painting it.Quote:
Originally Posted by mekanik
Are you comfortable that the concrete will have cured sufficiently, and is not gassing, prior to pouring the epoxy? I'm not going off anything other than tales that concrete takes a lot longer than some might expect.
Hey. I'm not 100% on the curing time but really just playing that by ear at the moment. The grinding process on the top is complete now and that proxess was useful in order to gauge the state of curing. Really messy job but was able to get it within a few mm across the surface. I plan to pour it toward this weekend which should be over three weeks since it was poured for it to cure so my hope is that will be sufficient. Once the epoxy is on top my hope is that any remaining drying will be allowed for by the sides and underneath that will still be open to the air. I'm aware I'm experimenting here though, so it could prove to be an issue, but ill give it a bash to see how it goes. One thing I'm certain of at this point is the strength is there, even with a diamond cup on the grinder I was barely able to grind away the top, slow going. Whether that means a lot in relation to off gasing is beyond my knowledge to be honest
Today is epoxy pour day (number one)
I decided to pour the top in two stages. Reason being I wanted to ensure the first layer goes on without a hitch and apparently it's good practice to do it this way.
Step one: I went through the form and sealed all the edges with a small amount of epoxy, allowing it to fully cure before keying it in with some sandpaper. Reasoning here was to be 100% sure that my expensive resin wasn't going to leak down the side of the form. I'm glad I did this first as I was able to spot a few problem areas that needed a couple of coats to seal.
Attachment 28605Attachment 28607
Step two: I was really concerned about the temperature inhibiting curing. The resin I have is documented to work best above 20 degrees C but will cause issues if the temp drops below 15 degrees. Daytime temps at the moment are above 15 so that isn't an issue but nighttime temps are dropping to 11 or so.
What I ended up doing is buying a garage fan heater and a 13A plug thermostat. By sealing the underneath section of the form with some ply and blowing the hot air in, the idea is to heat the mass of the concrete base and prevent any issues. I'm told the air temperature doesn't matter so much so long as the surface temp is above the threshold. This seemed like the most efficient way of getting the heat where it's needed without breaking the bank on electricity. We'll see if it works.
Attachment 28606Attachment 28604
I'm currently in and out of the workshop to pop any troublesome bubbles with a hot air gun, so far so good anyway.
Best, John
After 48 hours to cure the first layer of resin is on and cured.
I'm pretty happy with the result so far. One thing to note is that the concrete, being porous, caused many bubbles during the set up. The resin I have has a very long pot life: >8 hours @ 25C so I was in and out of the workshop every 30 minutes during that period to pop any bubbles as resin sank into the pores. It wasn't much hassle to be honest, the heat gun takes the bubbles out in a flash with a quick pass. Incidentally I should mention I have an adjustable heat gun (designed for reworking PCB's) so that was set to the lowest heat setting in order to avoid overheating the resin.
After cure I'm quite happy with the results, it's self levelled very well indeed. I have a sensitive Starett No 98 machinists level and it's no more that fractions of a mm off in the worst spots. I'm also glad I chose to do it in two stages, the porous nature of the concrete left some areas with creators as the resin sank into pores during the end of the pot life leaving small craters. At this stage it will be completely watertight so the next layer should even that out nicely.
I plan to leave it to cure for another day or so as I get on with other things following this I'll key it in lightly with some sandpaper, hoover up the dust and pour the second layer in the same way.
I've been thinking ahead to mounting the machine and have some materials on order for that which should be here soon.
Attachment 28621Attachment 28622Attachment 28623